I had this dish while in NYC and enjoyed it so much that I decided to recreate it at home. The thing that struck me about this preparation was the refined cleanliness of the flavor. Even more impressive is the fact that pork belly is involved...normally a very fatty piece of meat which can often taste heavy and overly rich. All in all, a success...George deems it the best pork belly dish that I've ever made.
A little bit about the name. Most people know that Japan was basically isolated from foreign influence until the mid 1800's. What I didn't realize was that the port of Nagasaki was already somewhat open having been a trading port for the Portuguese and Dutch. Through these outside influences, foreign foods, such as pork (illegal to slaughter due to Buddhist rules) made their way into Japan. There's your history lesson for the day.
Anyhow, I'm using Japanese Cooking A Simple Art which should be at the top of your list if you want to start learning about Japanese food. The author ran a cooking school in Japan so the instructions are very clearly written and directed towards people with little cooking experience. A great tome of knowledge.
Preheat oven to 300 degrees.
Pork! About a 2.5 pound slab of pork belly:
Slice into strips and then cubes. I took my slab of belly and cut it into the six strips you see below. I then cut each strip into four chunks:
Recipe said to brown the pork and then use hot water to rinse the pork of all extra fat. I was lazy so I deep-fried it...I figured it'd have the same effect. I did this in two batches.
Fried pork:
Rinsed pork:
Prepare the initial cooking broth. You need 2.5 cups of the water used when washing rice...you know how you rinse the water and it turns milky? Save 2.5 cups worth and add it to a large pot. Take two LARGE pieces (3 inches long) of ginger and scrape the peel off with a spoon. Cut into rough chunks and smash the chunks so they split/crack. Add all of the ginger to your pot which already has the rice water. Add the rinsed, browned pork. Add enough water to cover the pork generously.
Bring the water to a simmer, plop a lid on top and drop into the oven for a few hours...until tender. Took me about 2 hours.
When soft, scoop out the pork, set aside and throw away the water and ginger. Rinse the pork chunks...careful, they might be soft and fragile. Store overnight in the fridge.
The next day...combine 3.5 cups of dashi (i made mine with dashi-no-moto...buy this stuff, the author of this cookbook even acknowledges the excellence of the powdered product), 1 cup of sake, 2 tablespoons of mirin, 6 tablespoons of dark soy sauce and 6 tablespoons of sugar.
Place the ingredients in a pot and heat up to dissolve the sugar. Add the refrigerated pork and stir. Bring to a simmer and LIGHTLY cook for 30 minutes...don't simmer too vigorously because the pork is already soft...you don't want the pieces to disintegrate... 
Here's the end product:If you're like me, you will want to refrigerate the pork and sauce. The next day, you'll be able to skim off the remaining fat (shouldn't be much) and it will also taste better. Serve with rice and miso soup. You don't need much, maybe two chunks of pork per serving. Sauce is nicely sweet, a little salty...pork carries with it plenty of ginger flavor from the initial braise. Really, really tasty.Time- Pathetically easy. The most work you'll have to do is cut the pork into cubes. Takes about 5 minutes of active cooking time. The rest is simmering or frying. If you decide to brown the pork in a more traditional manner, it'll take a bit more effort.
Food cost-
Pork- $5.00
Small bottle of cheap sake- $4.00
Incidentals- $1.00
Total- $10.00
Will yield 12 two chunk portions or 8, three chunk portions. So around a dollar per serving.
